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The dark, firm and dry (DFD) or dark-cutting condition causes large losses to both the cattle feedlot and meat industry due to its unattractive, dark red colour and its limited shelf life. Dark-cutting, is a direct consequence of low muscle glycogen at slaughter and results in a lack of normal acidification of meat during rigor development causing high pH (>5.8). Glycogen breakdown in muscle may be rapidly triggered by increased circulating adrenaline or by strenuous muscular activity. Several other factors have also been found to lead to the DFD condition in cattle. The aims of this investigation were to determine the incidence of DFD in cattle slaughtered at a South African abattoir and to identify potential causative factors of this syndrome. It was furthermore also important to evaluate the sensory attributes, microbiological quality and hence, shelf life of DFD meat. The incidence of DFD carcasses, based on pH measurements (threshold ~ 5.8) within I h post mortem on 22 178 cattle in the M. longissimus dorsi, was 11.8%. The estimated overall incidence measured over a 5 -day period, testing only cattle supplied by the four main feedlots, was 7.83% (N= 5 659), measuring pH 24 (~5.8), confirmed by colour grades (values of 7 or 8 were classified as DFD). The incidence of dark-cutting beef, also seemed to be feedlot related with the highest being 12.37% and the lowest 1.75%. It is suspected that the incidence of DFD carcasses is higher in extremely hot or cold weather or large fluctuations, and should decrease during the months with milder temperatures. Transport distances did not affect the DFD incidence. In experiment 2, cattle from Feedlot C, transported over a short distance (45 km) had a higher incidence of DFD (9%) than those of Feedlot A (1.7%), transported over the longer distance of 290 km. Long holding periods in the holding pens at the abattoir (>24 h and even as high as 54 h), appeared not to have a significant influence on the occurrence of DFD. There was no correlation between bruised carcasses and DFD carcasses (the respective means of bruising were 6.7% and 3%, and respective mean incidences of DFD were 1.7% and 9%). Using Scheffe's test to compare the effect of gender on the incidence of DFD, significantly more bulls and steers were affected by dark-cutting than heifers (P< 0.0001). Mounting behaviour among young bulls, and social regrouping of steers during the pre-slaughter period, have been shown to increase the incidence of dark-cutting. Avoidance of mixing unfamiliar bulls and steers during transport and holding periods has been recommended to minimise stress. The low incidence of dark-cutters (P > 0.05) in heifers could possibly indicate a non-¬oestrus situation in the majority of the heifers, since a significant association between the presence of oestrus and DFD was shown previously by other researchers. The effect of gender on the incidence of dark-cutting, related to feedlot, was also significant. Higher incidences of DFD were found with steers of Feedlots B, C and 0 (14.5%, 11.6% and 13.7% respectively) than in Feedlot A (1.9%). The lowest overall incidence of dark-cutters was found in Feedlot A (1.7%). It appeared as if the breed type of the cattle had an effect on the dark-cutting beef. The Bos indicus (Brahman-type) animals had a significant effect (P< 0.001), on the colour of the beef when compared with European breeds. Cattle of two feedlots, fasted for periods of 40 hand 60 h, showed that a shorter fasting period had a significant effect (P < 0.001) on the pH. It appeared as if pre-slaughter stress, induced dark-cutting more readily in fasted than in fed cattle. Fasting also inhibited muscle glycogen re-synthesis during recovery of stress. The effect of pre-slaughter handling on the blood composition and muscle glycogen content of cattle of three different feedlots was studied. After transport (phase 1), the glycogen depletion was significant for all three feedlots (P < 0.05). Further glycogen depletion was found after slaughter (phase 2) (P < 0.01). The hematocrit increased after transport, which indicated that animals of Feedlot B (P < 0.0001) experienced stress. During the second phase, a significant decrease in hematocrit for Feedlot B was observed (P < 0.05). For Feedlot A, a non-significant increase was found in phase 1, with a significant (P < 0.05) increase in phase 2. The hematocrit of cattle of Feedlot C, however, showed a significant decrease during both phases. The blood glucose concentration for all three feedlots increased during phase 1, but was not significant. However, the blood glucose concentrations for all three feedlots increased significantly during phase 2 which probably indicated that the animals experienced stress during this period. The increase in creatine kinase was significant (P < 0.01) during both phases 1 and 2 for Feedlot A. Fluctuations were found in the creatine kinase concentrations of Feedlot C. Feedlot B, however, showed a significant decrease in the creatine kinase concentrations. Free fatty acid concentrations for all feedlots increased linearly over the different stages. The high free fatty acid concentrations in blood samples of phase 2, of Feedlots Band C confirmed that these animals experienced stress, especially from the period being held in the pens to after slaughter (P < 0.01 for both). The free fatty acid concentration, appear to be the best blood parameter to relate to meat quality. The DFD incidence during this experiment, for Feedlots Band C, is 35%. For Feedlot A, with the lowest DFD incidence (16%), the increase of free fatty acid concentration was not significant. Although the effect of growth promoters was not tested, the use of beta-agonists as growth promoters may increase the incidence of dark-cutting meat unless a sufficient withdrawal period before slaughter is observed. Feedlots A and C implanted Revelor in 9 month old cattle, while Feedlot B implanted both Synovex S (at 6 weeks) and Revelor (at 4 months). Consumer sensory evaluations indicated that the general appearance (P < 0.05), colour (P < 0.001) and acceptability (P < 0.01) of raw normal steak were preferred significantly to those of raw DFD steak. Twice as many panellists preferred the raw normal steak than raw DFD because of the more attractive red colour, compared to the almost black colour of raw DFD steak. The hedonic ratings of the sensory attributes of fried normal steak versus fried DFD steak were non-significant for all attributes, although it was expected that consumers would find the DFD steak more tender and less flavoursome than normal steak. DFD meat samples (N= 84) were tested over a 7-week period for total aerobic count, Pseudomonas, coliforms and Eschericia coli. Normal beef samples were expected to be acceptable, both on microbiological grounds and sensory evaluations until at least the seventh week. Microbiological spoilage of vacuum-packaged DFD meat took place during the second week and deterioration was more evident during the fourth week, due to the presence of cheesy odours. During the fifth week, green discolouration of the meat was observed. / Dissertation (MSc Agric (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

Bread flour quality, which is directly related bread quality, varies from time to time. It is therefore almost impossible to obtain bread with consistent quality without determining the flour's suitability for bread-making and the addition of bread improvers. Rheological tests such as the farinograph and the mixograph which are commonly used by bakeries to predict flour quality are empirical in nature which makes fundamental interpretation of the results difficult. The stress relaxation test, a more fundamental rheological test, was used in combination with the mixograph to determine if the stress relaxation test can provide additional information to the mixograph on prediction of the effect of ascorbic acid and DATEM on bread-making quality of three different flour samples. In this test, an optimally developed ball of dough was compressed between parallel plates of a TA-XT2 texture analyser. The 20 g dough was compressed to a load of 1.5 N and thereafter allowed to relax at constant deformation. The relaxation time (RT) was recorded as time taken for the compression force to decay to a force of 0.65 N. Longer RT indicated better flour quality. RT was compared with the mixograph peak time and peak height as predictors of the effect of ascorbic acid and DATEM on bread quality. Test bakes were carried out, and concentrations of ascorbic acid and DATEM were varied as in the stress relaxation test and the mixograph test. At the various stages of the baking process several dough and bread properties were assessed subjectively and scored according to a standardised scoring system. The mixograph was successful in characterising untreated flours in terms of bread-making quality and the stress relaxation test did not provide additional information in this regard. The mixograph was better able to predict the effect of improvers on the stronger Lelie while the stress relaxation test was better at predicting improver effect (especially of DATEM) on the weaker flours, Tiger and Silver Queen. The mixograph predicted the improving effect of DATEM on Tiger and Silver Queen up to a peak, followed by no further improvement. The stress relaxation test predicted improvement beyond the peak, and this continued improvement was observed in the test bake and strong correlation (p<O.05) was found between effect of DATEM on RTs and these important test bake parameters: baking height, loaf volume, drop baking height and the bread score. In addition to information on mixing properties provided by the mixograph, RT seemed to be predicting dough's stability, related to its gas-retaining properties. This stability which can be enhanced by DATEM may be related to both the extensibility of dough's gluten matrix and the stability of the liquid film surrounding the gluten matrix. / Dissertation (MSc (Agric) Food Science and Technology)--University of Pretoria, 2005. / Food Science / unrestricted

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Call number: LD2668 .T4 1979 H39 / Master of Science

1. A seed vigour test provides a more sensitive measurement of seed quality than the standard germination test. The cold test is one of the most widely used vigour tests for maize but procedures had not been standardized. In this study different cold test methods were compared for their usefulness as a seed vigour test. 2. Field emergence of 12 hybrid seed lots and 10 parent line seed lots were determined in four different field trials, representing different environmental conditions. Conditions were cold and wet, cool and wet, and favourable. Percentage emergence and emergence rates were determined for the different trials. 3. Considerable differences were found between percentage emergence in the different trials and the standard germination test results. The lowest emergence counts as well as emergence rates were obtained with the oldest seed lots. The differences found in emergence counts between the different seed lots appear to be the result of ageing and dete¬rioration and thus differences in vigour. The ranking order of the different seed lots according to percentage emergence were similar for the different trials. 4. Six different cold test methods and the standard germination test were conducted in the laboratory and the results of the different tests were correlated with field emergen¬ce. The deep-box and rolled towel methods were used and the germination substrates used were sand, a sand-soil mixture, vermiculite, a vermiculite-soil mixture and paper towels with and without soil. 5. Considerable differences were found in percentage emergence between the different laboratory tests. The lowest vigour percentages were obtained with the older seed lots, thus a decline in percentage emergence with an increase in age of the seed lot. The same tendency was found with the field emergence trials. The ranking order of the seed lots did not show large differences between the different tests. 6. Lower vigour percentages were obtained when soil was included in the germination medium and this effect was more pronounced with the older seed lots. The sand + soil cold test was found to be the strictest of the cold tests with the lowest percentage emergence. 7. Correlations were determined between the results of the different cold tests and emergence in the different field trials. All correlation coefficients of the hybrid seed lots were found to be significant at the 1 % level. However, the correlation coefficients obtained between the standard germination test and field emergence were generally of a lower order than those obtained with the cold tests. No significant correlations were 61 found between emergence and the germination percentages of the parent line seed lots. 8. Although the correlations between the different laboratory test results and field emergence do not provide ground for a clear recommendation of adoption of one cold test procedure over another, inclusion of soil in the germination medium resulted in a small increase in correlation coefficients. Correlation coefficients between emergence and the sand + soil cold test were the highest in most of the trials . 9. Although any of the cold tests which include soil in the medium appear to be suitable for adoption by South African seed laboratories, the vermiculite + soil test has advantages over the sand + soil and paper + soil tests. / Dissertation (MSc (Botany))--University of Pretoria, 2006. / Plant Science / unrestricted

This study examines what is significant for high quality of jeans, and what processes and factors affects the intrinsic quality of the jeans. Based on this, compilations of reclaim statistics was made and interviews and quality testing was conducted to see if high quality requirements is key to both produce jeans of good quality and to reduce the number of complaints.Quality management is an important part of the day-to-day business of a company and should permeate the entire organization and all processes. In order to create jeans withhigh quality, quality testing is an important part of a quality management. Quality tests are made to ensure that the products meet the demands and expectations on its properties. Quality tests also play an important role in the compilation and analysis of customer reclaims. Despite the quality and quality tests, there is a risk that dissatisfiedcustomers reclaim products they are not happy with. To relate customer claims against the quality of tests is a good way to evaluate what the problem is, or if it even is a problem.The study showed that high quality could be the solution to ensure the production of jeans with high quality. However, the problem is complex and therefore, the solution to reduce claims and high quality products to be something else or part of the solution. That goes for any company to be familiar with the underlying quality dimensions and based on that analyze where the critical points are found in their product development and manufacturing process.For the company of this study, the authors consider that the solution does not lie in raising quality requirements, but rather that the sewing should be improved and more quality control over garment measurement lists should be made. Quality tests cannot prove a lack of quality material and thus the authors consider that much of the claims are due to good will. / Program: Textilingenjörsutbildningen

Visual inspection of defects is an important part of quality assurance in many fields of production. It plays a very useful role in industrial applications in order to relieve human inspectors and improve the inspection accuracy and hence increasing productivity. Research has previously been done in defect classification of wood veneers using techniques such as neural networks, and a certain degree of success has been achieved. However, to improve results in tenus of both classification accuracy and running time are necessary if the techniques are to be widely adopted in industry, which has motivated this research. This research presents a method using rough sets based neural network with fuzzy input (RNNFI). Variable precision rough set (VPRS) method is proposed to remove redundant features utilising the characteristics of VPRS for data analysis and processing. The reduced data is fuzzified to represent the feature data in a more suitable foml for input to an improved BP neural network classifier. The improved BP neural network classifier is improved in three aspects: additional momentum, self-adaptive learning rates and dynamic error segmenting. Finally, to further consummate the classifier, a uniform design CUD) approach is introduced to optimise the key parameters because UD can generate a minimal set of uniform and representative design points scattered within the experiment domain. Optimal factor settings are achieved using a response surface (RSM) model and the nonlinear quadratic programming algorithm (NLPQL). Experiments have shown that the hybrid method is capable of classifying the defects of wood veneers with a fast convergence speed and high classification accuracy, comparing with other methods such as a neural network with fuzzy input and a rough sets based neural network. The research has demonstrated a methodology for visual inspection of defects, especially for situations where there is a large amount of data and a fast running speed is required. It is expected that this method can be applied to automatic visual inspection for production lines of other products such as ceramic tiles and strip steel.

In the current studied literature there is a lack of data and documentation on how outside factors affect the performance of ANC headphones. The purpose of this thesis is to investigate how these factors affect ANC headphone performance. The investigation into these factors was done by gathering quantitative data with experiments. The analysis method chosen was an ANOVA-inspired method that compared the differences found in the processed data. The results show that the sample variation between the number of speakers used did not differ by much. However, the variability in the samples collected using different noise types was noticeably higher while short noise resulted in odd-shaped graphs. When combining parameters from the different tests, effects such as graph shapes, seem to remain. These are the conclusions made. When testing with pink noise, the amount of speakers used and how long the pink noise is played makes a minimal difference for attenuation and variation. However, having more speakers and playing the sound for longer durations creates slightly more stable measurements. Unstable noise recordings are unsuitable for product quality testing due to the unreliable results they give. These noise recordings are still suitable for other research purposes.